Added middle button doubleclick, fixes #15567

(cherry picked from commit 0f00384c93e07c6612456de489067f2cb883ecee)

platform/windows/os_windows.cpp

@@ -461,6 +461,7 @@ LRESULT OS_Windows::WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 		case WM_MOUSEWHEEL:
 		case WM_MOUSEHWHEEL:
 		case WM_LBUTTONDBLCLK:
+		case WM_MBUTTONDBLCLK:
 		case WM_RBUTTONDBLCLK:
 			/*case WM_XBUTTONDOWN:
 		case WM_XBUTTONUP: */ {
@@ -521,6 +522,12 @@ LRESULT OS_Windows::WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 						mb.button_index = 2;
 						mb.doubleclick = true;
 					} break;
+					case WM_MBUTTONDBLCLK: {
+
+						mb.pressed = true;
+						mb.button_index = 3;
+						mb.doubleclick = true;
+					} break;
 					case WM_MOUSEWHEEL: {
 
 						mb.pressed = true;